A room measures 20′ x 40’and will have 2″ x 6″ ceiling joists placed at 16″o.c. The joists are 10′ long and the room will have a beam in the center. How many ceiling joists are needed?

A room measures 20′ x 40’and will have 2″ x 6″ ceiling joists placed at 16″o.c. The joists are 10′ long and the room will have a beam in the center. How many ceiling joists are needed?